Detection of target molecules is useful in many industries. For example, detection and quantification of biological molecules is a basis for disease diagnostics. Detection and/or purification can be performed using techniques that, at least in part, utilize differences in isoelectric point between target molecules and other molecules in a sample. Such methods include those that involve isoelectric focusing. Current isoelectric focusing based protein/peptide fractionation technologies suffer from at least two shortcomings. First, samples are separated over a fixed or limited pH range resulting in non-optimal fractionation of various samples. Second, pH gradients required for sample fractionation are established via chemicals (ampholytes) resulting in contamination of fractionated samples with chemicals and (potential) interference of downstream analysis.